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Posted by Boris Stumm on 06/01/07 09:38
David CZ wrote:
[...]
> SELECT products.id, products.name, tags.id
> FROM products INNER JOIN (tags, product_tag)
> ON (product_tag.product_id = products.id AND product_tag.tag_id =
> tags.id)
> WHERE products.id = 12;
The join with tags is not necessary.
> Which gives me two lines of results:
>
> 12 Product1 1
> 12 Product1 5
>
> I would like a result like this though:
>
> 12 Product1 1,5
Since you do not know how many tags a product has, this is
not possible (at least to my knowledge)
But that is not so much of a problem, you can do that in
your PHP code.
The only way I can think of, but I'd consider it a "dirty"
way, is the following:
* your tags are numbered 1, 2, 4, 8, ... This is possible
if you do not have too many tags, maybe maximum 32 or so
if you use 4-byte integers.
* Then, you can change the select to:
select p.id, p.name, sum(pt.tag_id) as tag_mask
from products p, product_tag pt
where p.id = pt.product_id
group by p.id, p.name
You will then have one tuple per product, with the
tags contained in the tag_mask.
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